Question

How many grams of fluorine are in 24.7 grams of NF3?

Answer 1

Molar mass of NF3,
MM = 1*MM(N) + 3*MM(F)
= 1*14.01 + 3*19.0
= 71.01 g/mol


mass(NF3)= 24.7 g

use:
number of mol of NF3,
n = mass of NF3/molar mass of NF3
=(24.7 g)/(71.01 g/mol)
= 0.3478 mol
This is number of moles of NF3

one mole of NF3 contains 3 mole of F
use:
number of moles of F = 3 * number of moles of NF3
= 3 * 0.3478
= 1.044

Molar mass of F = 19 g/mol

use:
mass of F,
m = number of mol * molar mass
= 1.044 mol * 19 g/mol
= 19.8 g
Answer: 19.8 g